Stitching of paths for improved text-on-path rendering of map labels

ABSTRACT

A wireless communications device obtains sets of map data for rendering portions of a map on a display of the device. The map data includes label data for rendering labels on the map for identifying map features. Once the map data is obtained, the wireless device generates a list of all the labels to be rendered on the map, and for each duplicated label in the list, determines whether the map features associated with the duplicated labels connect on the map. If the labels connect, the device then generates a reconstructed map feature and renders a single instance of the label for the map feature. Accordingly, a map feature, such as a path, can be rendered with a single label even if the map data for the map feature, including its associated labels, was transmitted over-the-air as discrete sets of data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 60/788,434 entitled “Methods and Apparatus forDynamically Labelling Map Objects in Visually Displayed Maps of MobileCommunication Devices” filed on Mar. 31, 2006 and from U.S. ProvisionalPatent Application No. 60/787,541 entitled “Method and System forDistribution of Map Content to Mobile Communication Devices” filed onMar. 31, 2006.

TECHNICAL FIELD

The present disclosure relates generally to wireless communicationsdevices and, in particular, to techniques for generating map content onwireless communications devices.

BACKGROUND

Wireless communications devices such as the BlackBerry™ by Research inMotion Limited enable users to download map content from web-based datasources such as BlackBerry Maps™, Google Maps™ or Mapquest™. Downloadedmap content is displayed on a small LCD display screen of the wirelesscommunications device for viewing by the user. The user can pan up anddown and side to side as well as zoom in or out. Due to the smalldisplay on the device and due to the limited over-the-air (OTA)bandwidth, there is a need to optimize the delivery and handling of themap data.

With the increasing availability of wireless communications deviceshaving onboard Global Positioning System (GPS) receivers for providinglocation-based services (LBS), the efficient delivery and handling ofmap data is increasingly important.

Map data, including label data for labelling map features, iscommunicated from map servers to wireless communications devices indiscrete portions which are assembled client-side to provide the mapcontent requested by the user. However, when reconstructing a map fromdiscrete portions of data, however, redundant labelling can occur iflabels associated with each portion of data are rendered for the samefeature. Furthermore, even if redundant labels are suppressed, the labelassociated with a reconstructed map feature cannot be placedaesthetically in the center of the reconstructed feature but rather isplaced in the center of one of the constituent elements of the feature.

Accordingly, a technique for efficiently and aesthetically labellingmaps reconstructed from discrete portions of downloaded data remainshighly desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present technology will becomeapparent from the following detailed description, taken in combinationwith the appended drawings, in which:

FIG. 1 is a block diagram schematically illustrating pertinentcomponents of a wireless communications device and of a wirelesscommunications network;

FIG. 2 is a more detailed block diagram of a wireless communicationsdevice;

FIG. 3A is a system diagram of network components which provide mappingfunctionality in the wireless communications devices of FIG. 1 and FIG.2;

FIG. 3B illustrates a message exchange between a wireless communicationsdevice and a map server for downloading map content to the wirelesscommunications device based on the system of FIG. 3A;

FIG. 3C is a diagram showing a preferred Maplet data structure;

FIG. 4 is a schematic depiction of a wireless network having anapplications gateway for optimizing the downloading of map data from mapservers to wireless communications devices;

FIG. 5 is a flowchart presenting steps of a method of displaying a mapon a wireless device by stitching together constituent path segments togenerate a reconstructed path having a single label associated with thereconstructed path;

FIG. 6 schematically depicts the potential problem of redundantlabelling that may be encountered when map features are rendered fromdiscrete sets of map data;

FIG. 7 schematically depicts the potential problems of having bothpoorly placed labels and highly constrained labels that may beencountered when map features are rendered from discrete sets of mapdata by blindly squelching duplicated labels;

FIG. 8 schematically depicts a process of stitching together pathsegments (and constituent elements of other map features) to createreconstructed paths (and map features);

FIG. 9A schematically depicts constructing a label list with link,vector, and flag information for efficiently stitching together the mapfeatures of FIG. 6;

FIG. 9B schematically depicts a process of determining whether anendpoint of one path associated with a duplicated label matches anendpoint of another path having the same duplicated label;

FIG. 9C schematically depicts a process of determining vectordirectionality for vector map data;

FIG. 10 is a screenshot of a street map of downtown Ottawa, Canadawithout stitching (reconstruction) of paths; and

FIG. 11 is a screenshot of a street map of downtown Ottawa, Canada withstitching (reconstruction) of paths.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

The present technology provides, in general, a method of rendering a mapon a display of a wireless communications device where the map data,including label data, is downloaded over-the-air in small, discreteportions or sets of data, each with its own label data for labellingfeatures of the map. The wireless device generates a list of all thelabels to be rendered on the map, and for each duplicated label in thelist, determines whether the map features associated with the duplicatedlabels connect or coincide on the map. If the map features associatedwith the duplicated labels do coincide, a map application running on thedevice then generates a reconstructed map feature and renders a single(preferably centrally-positioned) instance of the label for the mapfeature. Accordingly, a map feature, such as a path, can be renderedwith a single label even if the map data for the map feature, includingits associated labels, was transmitted over-the-air as discrete sets ofdata containing redundant labels.

Thus, an aspect of the present technology is a method of displaying amap on a wireless communications device. The method includes steps ofobtaining sets of map data for rendering portions of the map on adisplay of the device, the map data including label data for renderinglabels on the map for identifying one or more map features andgenerating a list of all the labels to be rendered on the map. For eachduplicated label in the list, the method entails determining whether themap features associated with the duplicated labels connect on the map.Finally, a reconstructed map feature is generated and a single instanceof the label is rendered for the map feature.

Another aspect of the present technology is a computer program productthat includes code adapted to perform the steps of the foregoing methodwhen the computer program product is loaded into memory and executed ona processor of a wireless communications device.

Yet another aspect of the present technology is a wirelesscommunications device for enabling a user of the device to display a mapon the device. The wireless device includes an input device for enablingthe user to cause the device to obtain map data for rendering the map tobe displayed on a display of the device, the map data including labeldata for rendering labels on the map for identifying one or more mapfeatures. The wireless communications device further includes a memoryfor storing code to instruct a processor to generate a list of all thelabels to be rendered on the map, determine, for each duplicated labelin the list, whether the map features associated with the duplicatedlabels connect on the map, generate a reconstructed map feature, andrender on the display of the device a single instance of the label forthe map feature.

The details and particulars of these aspects of the technology will nowbe described below, by way of example, with reference to the attacheddrawings.

FIG. 1 is a block diagram of a communication system 100 which includes awireless communications device 102 (also referred to as a mobilecommunications device) which communications through a wirelesscommunication network 104. For the purposes of the presentspecification, the expression “wireless communications device”encompasses not only a wireless handheld, cell phone or wireless-enabledlaptop but also any mobile communications device or portablecommunications device such as a satellite phone, wireless-enabled PDA orwireless-enabled MP3 player. In other words, for the purposes of thisspecification, “wireless” shall be understood as encompassing not onlystandard cellular or microwave RF technologies, but also any othercommunications technique that conveys data over the air using anelectromagnetic signal.

The wireless communications device 102 preferably includes a visualdisplay 112, e.g. an LCD screen, a keyboard 114 (or keypad), andoptionally one or more auxiliary user interfaces (UI) 116, each of whichis coupled to a controller 106. The controller 106 is also coupled toradio frequency (RF) transceiver circuitry 108 and an antenna 110.Typically, controller 106 is embodied as a central processing unit (CPU)which runs operating system software in a memory device (described laterwith reference to FIG. 2). Controller 106 normally controls the overalloperation of the wireless communications device 102, whereas signalprocessing operations associated with communications functions aretypically performed in the RF transceiver circuitry 108. Controller 106interfaces with the display screen 112 to display received information,stored information, user inputs, and the like. Keyboard/keypad 114,which may be a telephone-type keypad or a full QWERTY keyboard, isnormally provided for entering commands and data.

The wireless communications device 102 sends communication signals toand receives communication signals from network 104 over a wireless linkvia antenna 110. RF transceiver circuitry 108 performs functions similarto those of station 118 and Base Station Controller (BSC) 120,including, for example, modulation and demodulation, encoding anddecoding, and encryption and decryption. It will be apparent to thoseskilled in the art that the RF transceiver circuitry 108 will be adaptedto the particular wireless network or networks in which the wirelesscommunications device is intended to operate.

The wireless communications device 102 includes a battery interface 134for receiving one or more rechargeable batteries 132. Battery 132provides electrical power to electrical circuitry in the device 102, andbattery interface 134 provides for a mechanical and electricalconnection for battery 132. Battery interface 134 is couple to aregulator 136 which regulates power to the device. When the wirelessdevice 102 is fully operationally, an RF transmitter of RF transceivercircuitry 108 is typically keyed or turned on only when it is sending tonetwork, and is otherwise turned off to conserve resources. Similarly,an RF receiver of RF transceiver circuitry 108 is typically periodicallyturned off to conserve power until it is needed to receive signals orinformation (if at all) during designated time periods.

Wireless communications device 102 operates using a Subscriber IdentityModule (SIM) 140 which is connected to or inserted in the wirelesscommunications device 102 at a SIM interface 142. SIM 140 is one type ofa conventional “smart card” used to identify an end user (or subscriber)of wireless device 102 and to personalize the device, among otherthings. Without SIM 140, the wireless communications device 102 is notfully operational for communication through wireless network 104. Byinserting the SIM card 140 into the wireless communications device 102,an end user can have access to any and all of his subscribed services.SIM 140 generally includes a processor and memory for storinginformation. Since SIM 140 is coupled to SIM interface 142, it iscoupled to controller 106 through communication lines 144. In order toidentify the subscriber, SIM 140 contains some user parameters such asan International Mobile Subscriber Identity (IMSI). An advantage ofusing SIM 140 is that end users are not necessarily bound by any singlephysical wireless device. SIM 140 may store additional user informationfor the wireless device as well, including datebook (calendar)information and recent call information.

The wireless communications device 102 may consist of a single unit,such as a data communication device, a cellular telephone, a GlobalPositioning System (GPS) unit, a multiple-function communication devicewith data and voice communication capabilities, a wireless-enabledpersonal digital assistant (PDA), or a wireless-enabled laptop computer.Alternatively, the wireless communications device 102 may be amultiple-module unit comprising a plurality of separate components,including but in no way limited to a computer or other device connectedto a wireless modem. In particular, for example, in the block diagram ofFIG. 1, RF circuitry 108 and antenna 110 may be implemented as a radiomodem unit that may be inserted into a port on a laptop computer. Inthis case, the laptop computer would include display 112, keyboard 114,one or more auxiliary UIs 116, and controller 106 embodied as thecomputer's CPU.

The wireless communications device 102 communicates in and through awireless communication network 104. The wireless communication networkmay be a cellular telecommunications network. In the example presentedin FIG. 1, wireless network 104 is configured in accordance with GlobalSystems for Mobile communications (GSM) and General Packet Radio Service(GPRS) technologies. Although wireless communication network 104 isdescribed herein as a CSM/GPRS-type network, any suitable networktechnologies may be utilized such as Code Division Multiple Access(CDMA), Wideband CDMA (WCDMA), whether 2G, 3G, or Universal MobileTelecommunication System (UMTS) based technologies. In this example, theGSM/GPRS wireless network 104 includes a base station controller (BSC)120 with an associated tower station 118, a Mobile Switching Center(MSC) 122, a Home Location Register (HER) 132, a Serving General PacketRadio Service (GPRS) Support Node (SGSN) 126, and a Gateway GPRS SupportNode (GGSN) 128. MSC 122 is coupled to BSC 120 and to a landlinenetwork, such as a Public Switched Telephone Network (PSTN) 124. SGSN126 is coupled to BSC 120 and to GGSN 128, which is, in turn, coupled toa public or private data network 130 (such as the Internet). HELR 132 iscoupled to MSC 122, SGSN 126 and GGSN 128.

Tower station 118 is a fixed transceiver station. Tower station 118 andBSC 120 may be referred to as transceiver equipment. The transceiverequipment provides wireless network coverage for a particular coveragearea commonly referred to as a “cell”. The transceiver equipmenttransmits communication signals to and receives communication signalsfrom wireless communications devices 102 within its cell via station118. The transceiver equipment normally performs such functions asmodulation and possibly encoding and/or encryption of signals to betransmitted to the wireless communications device in accordance withparticular, usually predetermined, communication protocols andparameters. The transceiver equipment similar demodulates and possiblydecodes and decrypts, if necessary, any communication signals receivedfrom the wireless communications device 102 transmitting within itscell. Communication protocols and parameters may vary between differentnetworks. For example, one network may employ a different modulationscheme and operate at different frequencies than other networks.

The wireless link shown in communication system 100 of FIG. 1 representsone or more different channels, typically different radio frequency (RF)channels, and associated protocols used between wireless network 104 andwireless communications device 102. An RF channel is a limited resourcethat must be conserved, typically due limits in overall bandwidth and alimited battery power of the wireless device 102. Those skilled in theart will appreciate that a wireless network in actual practice mayinclude hundreds of cells, each served by a station 118, depending upondesired overall expanse of network coverage. All pertinent componentsmay be connected by multiple switches and routers (not shown),controlled by multiple network controllers.

For all wireless communications devices 102 registered with a networkoperator, permanent data (such as the user profile associated with eachdevice) as well as temporary data (such as the current location of thedevice) are stored in the HLR 132. In case of a voice call to thewireless device 102, the HLR 132 is queried to determine the currentlocation of the device 102. A Visitor Location Register (VLR) of MSC 122is responsible for a group of location areas and stores the data ofthose wireless devices that are currently in its area of responsibility.This includes parts of the permanent data that have been transmittedfrom HLR 132 to the VLR for faster access. However, the VLR of MSC 122may also assign and store local data, such as temporary identifications.Optionally, the VLR of MSC 122 can be enhanced for more efficientco-ordination of GPRS and non-GPRS services and functionality (e.g.paging for circuit-switched calls which can be performed moreefficiently via SGSN 126, and combined GPRS and non-GPRS locationupdates).

Serving GPRS Support Node (SGSN) 126 is at the same hierarchical levelas MSC 122 and keeps track of the individual locations of wirelessdevices 102. SGSN 126 also performs security functions and accesscontrol. Gateway GPRS Support Node (GGSN) 128 provides internetworkingwith external packet-switched networks and is connected with SGSNs (suchas SCSN 126) via an IP-based GPRS backbone network. SGSN 126 performsauthentication and cipher setting procedures based on the samealgorithms, keys, and criteria as in existing GSM. In conventionaloperation, cell selection may be performed autonomously by wirelessdevice 102 or by the transceiver equipment instructing the wirelessdevice to select a particular cell. The wireless device 102 informswireless network 104 when it reselects another cell or group of cells,known as a routing area.

In order to access GPRS services, the wireless device 102 first makesits presence known to wireless network 104 by performing what is knownas a GPRS “attach”. This operation establishes a logical link betweenthe wireless device 102 and SGSN 126 and makes the wireless device 102available to receive, for example, pages via SGSN, notifications ofincoming GPRS data, or SMS messages over GPRS. In order to send andreceive GPRS data, the wireless device 102 assists in activating thepacket data address that it wants to use. This operation makes thewireless device 102 known to GCSN 128; internetworking with externaldata networks can thereafter commence. User data may be transferredtransparently between the wireless device 102 and the external datanetworks using, for example, encapsulation and tunnelling. Data packetsare equipped with GPRS-specific protocol information and transferredbetween wireless device 102 and GGSN 128.

Those skilled in the art will appreciate that a wireless network may beconnected to other systems, possibly including other networks, notexplicitly shown in FIG. 1. A network will normally be transmitting atvery least some sort of paging and system information on an ongoingbasis, even if there is no actual packet data exchanged. Although thenetwork consists of many parts, these parts all work together to resultin certain behaviours at the wireless link.

FIG. 2 is a detailed block diagram of a preferred wirelesscommunications device 202. The wireless device 202 is preferably atwo-way communication device having at least voice and advanced datacommunication capabilities, including the capability to communicate withother computer systems. Depending on the functionality provided by thewireless device 202, it may be referred to as a data messaging device, atwo-way pager, a cellular telephone with data message capabilities, awireless Internet appliance, or a data communications device (with orwithout telephony capabilities). The wireless device 202 may communicatewith any one of a plurality of fixed transceiver stations 200 within itsgeographic coverage area.

The wireless communications device 202 will normally incorporate acommunication subsystem 211, which includes a receiver 212, atransmitter 214, and associated components, such as one or more(preferably embedded or internal) antenna elements 216 and 218, localoscillators (LO's) 213, and a processing module such as a digital signalprocessor (DSP) 220. Communication subsystem 211 is analogous to RFtransceiver circuitry 108 and antenna 110 shown in FIG. 1. As will beapparent to those skilled in the field of communications, the particulardesign of communication subsystem 211 depends on the communicationnetwork in which the wireless device 202 is intended to operate.

The wireless device 202 may send and receive communication signals overthe network after required network registration or activation procedureshave been completed. Signals received by antenna 216 through the networkare input to receiver 212, which may perform common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection, and the like, and, as shown in the example of FIG. 2,analog-to-digital (A/D) conversion. A/D conversion of a received signalallows more complex communication functions such as demodulation anddecoding to performed in the DSP 220. In a similar manner, signals to betransmitted are processed, including modulation and encoding, forexample, by DSP 220. These DSP-processed signals are input totransmitter 214 for digital-to-analog (D/A) conversion, frequency upconversion, filtering, amplification and transmission over communicationnetwork via antenna 218. DSP 220 not only processes communicationsignals, but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 212 andtransmitter 214 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 220.

Network access is associated with a subscriber or user of the wirelessdevice 202, and therefore the wireless device requires a SubscriberIdentity Module or SIM card 262 to be inserted in a SIM interface 264 inorder to operate in the network. SIM 262 includes those featuresdescribed in relation to FIG. 1. Wireless device 202 is abattery-powered device so it also includes a battery interface 254 forreceiving one or more rechargeable batteries 256. Such a battery 256provides electrical power to most if not all electrical circuitry in thedevice 102, and battery interface provides for a mechanical andelectrical connection for it. The battery interface 254 is coupled to aregulator (not shown) which provides a regulated voltage V to all of thecircuitry.

Wireless communications device 202 includes a microprocessor 238 (whichis one implementation of controller 106 of FIG. 1) which controlsoverall operation of wireless device 202. Communication functions,including at least data and voice communications, are performed throughcommunication subsystem 211. Microprocessor 238 also interacts withadditional device subsystems such as a display 222, a flash memory 224,a random access memory (RAM) 226, auxiliary input/output (I/O)subsystems 228, a serial port 230, a keyboard 232, a speaker 234, amicrophone 236, a short-range communications subsystem 240, and anyother device subsystems generally designated at 242. Some of thesubsystems shown in FIG. 2 perform communication-related functions,whereas other subsystems may provide “resident” or on-board functions.Notably, some subsystems, such as keyboard 232 and display 222, forexample, may be used for both communication-related functions, such asentering a text message for transmission over a communication network,and device-resident functions such as a calculator or task list.Operating system software used by the microprocessor 238 is preferablystored in a persistent (non-volatile) store such as flash memory 224,which may alternatively be a read-only memory (ROM) or similar storageelement (not shown). Those skilled in the art will appreciate that theoperating system, specific device applications, or parts thereof, may betemporarily loaded into a volatile store such as RAM 226.

Microprocessor 238, in addition to its operating system functions,enables execution of software applications on the wireless device 202. Apredetermined set of applications which control basic device operations,including at least data and voice communication applications, willnormally be installed on the device 202 during its manufacture. Forexample, the device may be pre-loaded with a personal informationmanager (PIM) having the ability to organize and manage data itemsrelating to the user's profile, such as e-mail, calendar events, voicemails, appointments, and task items. Naturally, one or more memorystores are available on the device 202 and SIM 256 to facilitate storageof PIM data items and other information.

The PIM application preferably has the ability to send and receive dataitems via the wireless network. PIM data items may be seamlesslyintegrated, synchronized, and updated via the wireless network, with thewireless device user's corresponding data items stored and/or associatedwith a host computer system thereby creating a mirrored host computer onthe wireless device 202 with respect to such items. This is especiallyadvantageous where the host computer system is the wireless deviceuser's office computer system. Additional applications may also beloaded into the memory store(s) of the wireless communications device202 through the wireless network, the auxiliary I/O subsystem 228, theserial port 230, short-range communications subsystem 240, or any othersuitable subsystem 242, and installed by a user in RAM 226 or preferablya non-volatile store (not shown) for execution by the microprocessor238. Such flexibility in application installation increases thefunctionality of the wireless device 202 and may provide enhancedonboard functions, communication-related functions or both. For example,secure communication applications may enable electronic commercefunctions and other such financial transactions to be performed usingthe wireless device 202.

In a data communication mode, a received signal such as a text message,an e-mail message, or a web page download will be processed bycommunication subsystem 211 and input to microprocessor 238.Microprocessor 238 will preferably further process the signal for outputto display 222 or alternatively to auxiliary I/O device 228. A user ofthe wireless device 202 may also compose data items, such as emailmessages, for example, using keyboard 232 in conjunction with display222 and possibly auxiliary I/O device 228. Keyboard 232 is preferably acomplete alphanumeric keyboard and/or telephone-type keypad. Thesecomposed items may be transmitted over a communication network throughcommunication subsystem 211.

For voice communications, the overall operation of the wirelesscommunications device 202 is substantially similar, except that thereceived signals would be output to speaker 234 and signals fortransmission would be generated by microphone 236. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the wireless device 202. Although voice or audiosignal output is preferably accomplished primarily through speaker 234,display 222 may also be used to provide an indication of the identity ofthe calling party, duration on a voice call, or other voice call relatedinformation, as some examples.

Serial port 230 in FIG. 2 is normally implemented in a personal digitalassistant (PDA)-type communication device for which synchronization witha user's desktop computer is a desirable, albeit optional, component.Serial port 230 enables a user to set preferences through an externaldevice or software application and extends the capabilities of wirelessdevice 202 by providing for information or software downloads to thewireless device 202 other than through the wireless network. Thealternate download path may, for example, be used to load an encryptionkey onto the wireless device 202 through a direct and thus reliable andtrusted connection to thereby provide secure device communications.

Short-range communications subsystem 240 of FIG. 2 is an additionaloptional component which provides for communication between mobilestation 202 and different systems or devices, which need not necessarilybe similar devices. For example, subsystem 240 may include an infrareddevice and associated circuits and components, or a Bluetooth™communication module to provide for communication with similarly-enabledsystems and devices. Bluetooth™ is a trademark of Bluetooth SIG, Inc.

FIG. 3A is a system diagram of network components which provide mappingfunctionality in the wireless communication devices of FIGS. 1 and 2. Toachieve this, a mapping application is also provided in memory of thewireless communications device for rendering visual maps in its display.Wireless communications devices 202 are connected over a mobile carriernetwork 303 for communication through a firewall 305 to a relay 307. Arequest for map data from any one of the wireless communications devices202 is received at relay 307 and passed via a secure channel 309 throughfirewall 311 to a corporate enterprise server 313 and corporate mobiledata system (MDS) server 315. The request is then passed via firewall317 to a public map server and/or to a public location-based service(LBS) server 321 which provides location-based services (LBS) to handlethe request. The network may include a plurality of such map serversand/or LBS servers where requests are distributed and processed througha load distributing server. The map/LBS data may be stored on thisnetwork server 321 in a network database 322, or may be stored on aseparate map server and/or LBS server (not shown). Private corporatedata stored on corporate map/LBS server 325 may be added to the publicdata via corporate MDS server 315 on the secure return path to thewireless device 202. Alternatively, where no corporate servers areprovided, the request from the wireless device 202 may be passed viarelay 307 to a public MDS server 327, which sends the request to thepublic map/LBS server 321 providing map data or other local-basedservice in response to the request. For greater clarity, it should beunderstood that the wireless devices can obtain map data from a “pure”map server offering no location-based services, from an LBS serveroffering location-based services in addition to map content, or from acombination of servers offering map content and LBS.

A Maplet data structure is provided that contains all of the graphic andlabelled content associated with a geographic area (e.g. map featuressuch as restaurants (point features), streets (line features) or lakes(polygon features)). Maplets are structured in Layers of Data Entries(“DEntries”) identified by a “Layer ID” to enable data from differentsources to be deployed to the device and meshed for proper rendering.Each DEntry is representative of one or more artefact or label (or acombination of both) and includes coordinate information (also referredto as a “bounding box” or “bounding area”) to identify the area coveredby the DEntry and a plurality of data points that together represent theartefact, feature or label. For example, a DEntry may be used torepresent a street on a city map (or a plurality of streets), whereinthe carious points within the DEntry are separated into different partsrepresenting various portions of the artefact or map feature (e.g.portions of the street). A wireless device may issue a request for themap server to download only those DEntries that are included within aspecified area or hounding box representing an area of interest that canbe represented by, for example, a pair of bottom left, top rightcoordinates.

As depicted in FIG. 3B, the wireless communications device issues one ormore AOI (Area of Interest) requests, DEntry or data requests and MapletIndex requests to the map server for selective downloading of map databased on user context. Thus, rather than transmitting the entire mapdata for an area in reply to each request from the device (which burdensthe wireless link), local caching may be used in conjunction withcontext filtering of map data on the server. For example, if a user'swireless device is GPS enabled and the user is traveling in anautomobile at 120 km/h along a freeway then context filtering can byemployed to prevent downloading of map data relating to passing sidestreets. Or, if the user is traveling in an airplane at 30,000 feet,then context filtering can be employed to prevent downloading of mapdata for any streets whatsoever. Also, a user's context can be defined,for example, in terms of occupation, e.g. a user whose occupation is atransport truck driver can employ context filtering to preventdownloading of map data for side streets on which the user's truck isincapable of traveling, or a user whose occupation is to replenishsupplied of soft drink dispensing machines can employ context filteringto download public map data showing the user's geographical area ofresponsibility with irrelevant features such as lakes and parks filteredout and private map data containing the location of soft drinkdispensing machines superimposed on the public map data.

The Maplet Index request results in a Maplet Index (i.e. only a portionof the Maplet that provides a table of contents of the map dataavailable within the Maplet rather than the entire Maplet) beingdownloaded from the map server to the device, thereby conserving OTA(Over-the-Air) bandwidth and device memory caching requirements. TheMaplet Index conforms to the same data structure as a Maplet, but omitsthe data points. Consequently, the Maplet Index is small (e.g. 300-400bytes) relative to the size of a fully populated Maplet or aconventional bit map, and includes DEntry bounding boxes and attributes(size, complexity, etc.) for all artefacts within the Maplet. As thefield of view changes (e.g. for a location-aware device that displays amap while moving), the device (client) software assesses whether or notit needs to download additional data from the server. Thus, if the sizeattribute or complexity attribute of an artefact that has started tomove into the field of view of the device (but is not yet beingdisplayed) is not relevant to the viewer's current context, then thedevice can choose not to display that portion of the artifact. On theother hand, if the portion of the artefact is appropriate for display,then the device accesses its cache to determine whether the DEntriesassociated with that portion of the artefact have already beendownloaded, in which case the cached content is displayed. Otherwise,the device issues a request for the map server to download all the ofthe DEntries associated with the artifact portion.

By organizing the Maplet data structure in Layers, it is possible toseamlessly combine and display information obtained from public andprivate databases. For example, it is possible for the device to displayan office building at a certain address on a street (e.g. a 1^(st)z-order attribute from public database), adjacent a river (e.g. a 2^(nd)z-order attribute from public database), with a superimposed floor planeof the building to show individual offices (e.g. 11^(th) z-orderattribute from a private database, accessible through a firewall).

Referring back to FIG. 3A, within the network having map server(s)and/or LBS server(s) 321 and database(s) 322 accessible to it, all ofthe map data for the entire world is divided and stored as a gridaccording to various levels of resolution (zoom), as set forth below inTable A. Thus, a single A-level Maplet represents a 0.05×0.05 degreegrid area; a single B-level Maplet represents a 0.5×0.5 degree gridarea; a single C-level Maplet represents a 5×5 degree grid area; asingle D-level Maplet represents a 50×50 degree grid area; and a singleE level Maplet represents the entire world in a single Maplet. It isunderstood that Table A is only an example of a particular Maplet griddivision; different grid divisions having finer or coarser granularitymay, of courser, be substituted. A Maplet includes a set of layers, witheach layer containing a set of DEntries, and each DEntry containing aset of data points. TABLE A # of Maplets # of Maplets # of Maplets Gridto cover to cover to cover Level (degrees) the World North AmericaEurope A 0.05 × 0.05 25,920,000 356,000 100,000 B 0.5 × 0.5 259,2006,500 1000 C 5 × 5 2,592 96 10 D 50 × 50 32 5 5 E World 1 1 1

As mentioned above, three specific types of requests may be generated bya wireless communications device (i.e. the client)—AOI requests, DEntryrequests and Maplet Index requests. The requests may be generatedseparately or in various combinations, as discussed in greater detailbelow. An AOI (area of interest) request calls for all DEntries in agiven area (bounding box) for a predetermined or selected set of z-orderLayers. The AOI request is usually generated when the device moves to anew area so as to fetch DEntries for display before the device clientknows what is available in the Maplet. The Maplet Index has the exactsame structure as a Maplet but does not contain complete DEntries (i.e.the data Points actually representing artifacts and labels are omitted).Thus, a Maplet Index defines what Layers and DEntries are available fora given Maplet. A data or DEntry request is a mechanism to bundletogether all of the required Dentries for a given Maplet.

Typically, AOI and Maplet Index requests are paired together in the samemessage, although they need not be, while DEntry requests are generatedmost often. For example, when a wireless device moves into an area forwhich no information has been stored on the device client, the MapletIndex request returns a Maplet Index that indicates what data the clientcan specifically request from the server 321, while the AOI requestreturns any DEntries within the area of interest for the specifiedLayers (if they exist). In the example requests shown on FIG. 3B, thedesired Maplet is identified within a DEntry request by specifying thebottom-left Maplet coordinate. In addition, the DEntry request mayinclude a layer mask so that unwanted Layers are not downloaded, aDEntry mask so that unwanted data Points are not downloaded, and zoomvalues to specify a zoom level for the requested DEntry. Once the deviceclient has received the requested Maplet Index, the client typicallythen issues multiple DEntry requests to ask for specific DEntries (sincethe client knows all of the specific DEntries that are available basedon the Maplet Index).

In this particular implementation, a collection of 20×20 A-level Maplets(representing a 1×1 degree square) is compiled into a Maplet Block File(.mbl). An .mbl file contains a header which specifies the offset andlength of each Maplet in the .mbl file. The same 20×20 collection ofMaplet index data is compiled into a Maplet Index file (.mbx). The .mbland .mbx file structures are set forth in Tables B and C, respectively.TABLE B Address Offset Offset Length 0x000 Maplet #0 Offset Maplet #0Length (4 bytes) (4 bytes) 0x008 Maplet #1 Offset Maplet #1 Length 0x010Maplet #2 Offset Maplet #2 Length . . . . . . . . . 0xC78 Maplet #399Maplet #399 Offset Length 0xC80 Beginning of Maplet #0 0xC80 + Size ofMaplet #0 Beginning of Maplet #1 0xC80 + Size of Maplet #0 + #1Beginning of Maplet #2 . . . . . . 0xC80 + Σ of Size of Beginning ofMaplet #399 Maplets (#0:#398)

In Table B, the offset of Maplet #0 is 0x0000_(—)0000 since, in thisparticular example, the data structure is based on the assumption thatthe base address for the actual Maplet data is 0x0000_(—)0C80. Thereforethe absolute address for Maplet #0 data is: Maplet #0 Address=BaseAddress (0x0000_(—)0C80)+Maplet #0 Offset (0x0000_(—)0000), andadditional Maplet addresses are calculated as: Maplet #(n+1)Offset=Maplet #(n) Offset+Maplet #(n) Length. If a Maplet has no data ordoes not exist, the length parameter is set to zero (0x0000_(—)0000).TABLE C Address Offset Offset (4 bytes) Length (4 bytes) 0x000 MapletIndex #0 Maplet Index #0 Offset Length 0x008 Maplet Index #1 MapletIndex #1 Offset Length 0x010 Maplet Index #2 Maplet Index #2 OffsetLength . . . . . . . . . 0xC78 Maplet Index #399 Maplet Index #399Offset Length 0xC80 Beginning of Maplet Index #0 0xC80 + Size ofBeginning of Maplet Index #1 Maplet Index #0 0xC80 + Size of Beginningof Maplet Index #2 Maplet Index #0 + #1 . . . . . . 0xC80 + Σ ofBeginning of Maplet Index #399 Size of Maplet Indices (#0:#399)

In Table C, the offset of Maplet Index #0 is 0x0000_(—)0000 since,according to an exemplary embodiment the data structure is based on theassumption that the base address for the actual Maplet index data is0x0000_(—)0C80. Therefore, the absolute address for Maplet Index #0 datais: Maplet Index #0 Address=Base Address (0x0000_(—)0C80)+Maplet Index#0 Offset (0x0000_(—)0000), and additional Maplet index addresses arecalculated as: Maplet Index #(n+1) Offset=Maplet Index #(n)Offset+Maplet Index #(n) Length. If a Maplet Index has no data or doesnot exist, the length parameter is set to zero (0x0000_(—)0000).

FIG. 3C and Table D (below), in combination, illustrate, by way ofexample only, a basic Maplet data structure. Generally, as noted above,the Maplet data structure can be said to include a Maplet Index (i.e. anindex of the DEntries, each of which is representative of either anartifact or a label or both) together with data Points for each DEntrythat actually form such artifacts and labels. In this example, eachMaplet includes a Map ID (e.g. 0xA1B1C1D1), the # of Layers in theMaplet, and a Layer Entry for each Layer. The Map ID identifies the dataas a valid Maplet, and according to one alternative, may also be used toidentify a version number for the data. The # of Layers is an integerwhich indicates the number of Layers (and therefore Layer Entries) inthe Maplet. Each Layer Entry defines rendering attributes and isfollowed by a list of DEntries for each Layer. The above forms a MapletIndex. For a complete Maplet, each DEntry contains a set of data Points(referred to herein as oPoints) or Labels). It will be noted that Layerscan have multiple DEntries and the complete list of DEntries and Pointsare grouped by Layer and separated by a Layer Separator (e.g. hex value0xEEEEEEEE). In this example, each Layer Entry is 20 bytes long, and aDEntry is 12 bytes long. However, the number of Layers, number ofDEntries per Layer and the number of Points per DEntry depends on themap data and is generally variable.

Table D provides a high “byte-level” description of a Maplet for thisexample. TABLE D Data Quantity Total # of Bytes Map ID 1 4 bytes # ofLayers 1 4 bytes Layer Entries # of 20 bytes × (# of Layers) LayersDEntry of a x (# of # of 12 bytes × (Σ of the # Layer DEntries Layers ofDEntries in each in a Layer) + Points for Layer) 4 bytes × (Σ of the #of DEntry of a Points in each DEntry in Layer each Layer) + LayerSeparator 4 bytes × (# of Layers)

By way of a further example, the wireless network 200 depicted in FIG. 4can include an applications gateway (AG) 350 for optimizing data flowfor onboard applications such as a mapping application 500 stored inmemory (e.g. stored in a flash memory 224) and executable by themicroprocessor 238 of the wireless device 202.

As shown in FIG. 4, the wireless network 200 hosts a plurality ofhandheld wireless communications devices 202 (such as the BlackBerry™ byResearch in Motion Limited) having voice and data capabilities (for bothe-mail and web browsing) as well as a full QWERTY keyboard. Thesewireless communications devices 202 can access Web-based map data onpublic map servers 400 hosted on the Internet or other data network 130via the applications gateway (AG) 350 which mediates and optimizes dataflow between the wireless network 200 and the data network by performingvarious mappings, compressions and optimizations on the data.

The map server extracts generic map content from a GeographicalInformation Systems (GIS) map database (e.g. Navtech®, TelAtlas®, etc.)at a specified level of resolution (zoom level). Custom graphicsassociated with the query, such as highlighted route, pushpin forcurrent position or street address, etc. are post-processed and mergedby the server with the generic map content. Relevant screen graphics arethen labelled, and the merged map graphic is compressed and delivered tothe device for display.

In operation, a user of the wireless communications device 202 uses aninput device such as keyboard 232 and/or thumbwheel 233 to cause themicroprocessor 238 to open the map application 500 stored in the memory224. Using the keyboard 232 and thumbwheel 233, the user specifies a maplocation on the map application 500. In response to thisrequest/command, the microprocessor 238 instructs the RF transceivercircuitry 211 to transmit the request over the air through the wirelessnetwork 104. The request is processed by the AG 350 and forwarded intothe data network (Internet) using standard packet-forwarding protocolsto one or more of the public and/or private map servers 400, 410.Accessing a private map server 410 behind a corporate firewall 420 wasdescribed above with reference to FIG. 3A. Map data downloaded fromthese one or more map servers 400, 410 is then forwarded in data packetsthrough the data network and mapped/optimized by the AS 350 for wirelesstransmission through the wireless network 104 to the wirelesscommunications device 202 that originally sent the request.

The downloaded map data can be cached locally in RAM 226, and displayedon the display 222 or graphical user interface (GUI) of the device afterthe map application 500 reconstructs or “stitches together” portions offeatures or constituent path segments to generate a reconstructed mapfeature or path, as will elaborated below, so that a single instance ofthe label can be centrally rendered for the reconstructed feature orpath (provided it does not collide with another label of higherpriority). If a further request is made by the user (or if the userwants a change in the field of view by zooming or panning), the devicewill check whether the data required can be obtained from the localcache (RAM 226). If not, the device issues a new request to the one ormore map servers 400, 410 in the same manner as described above.

As described earlier, map data can optionally be downloaded first as aMaplet Index enabling the user to then choose which DEntries listed inthe Index to download in full. Furthermore, as described earlier, themap application can include user-configurable context filtering thatenables the user to filter out unwanted map features or artifacts by notdownloading specific DEntries corresponding to those unwanted mapfeatures or artifacts.

As a variant, the wireless communications device can optionally includea Global Positioning System (GPS) receiver (“GPS chip”) 550 forproviding location-based services (LBS) to the user in addition to mapcontent. Embedding a GPS chip 550 capable of receiving and processingsignals from UPS satellites enable the GPS chip to generate latitude andlongitude coordinates, thus making the device “location aware”. Toobtain local-based services, the map application within the wirelesscommunications device sends a request to the map server for informationrelating to a city, restaurant, street address, route, etc. If thedevice is “location aware”, the request would include the currentlocation of the device.

In lieu of, or in addition to, GPS coordinates, the location of thedevice can be determined using triangulation of signals from in-rangebase towers, such as used for Wireless E911. Wireless Enhanced 911services enable a cell phone or other wireless device to be locatedgeographically using radiolocation techniques such as (i) angle ofarrival (AOA) which entails locating the caller at the point wheresignals from two towers intersect; (ii) time difference of arrival(TDOA), which uses multilateration like GPS, except that the networksdetermine the time difference and therefore the distance from eachtower; and (iii) location signature, which uses “fingerprinting” tostore and recall patterns (such as multipath) which mobile phone signalsexhibit at different locations in each cell.

Operation of the systems described above will now be described withreference to the method steps depicted in the flowchart of FIG. 5. Asdepicted in FIG. 5, this method of displaying a map on a wirelesscommunications device includes initial steps of opening the mapapplication on the device (step 600) and specifying an area of interest(AOI) using the map application (step 602), e.g. specifying a streetaddress, coordinates of latitude or longitude, or clicking on a locationon a world map, etc. In response to the specifying of an AOI, map datais then obtained (step 604) for rendering the map to be displayed on thewireless communications device. For the purposes of this specification,“obtaining map data” means receiving or downloading the map data overthe air, i.e. over a wireless link, retrieving the map data from a localcache, or downloading the map data over a wired connection, or anycombination thereof. In other words, as depicted in FIG. 5, obtainingmap data includes steps of determining whether the data is alreadycached locally (step 604). If the data is locally cached, the map datais retrieved from the cache (step 606). Otherwise, if not all of the mapdata is cached, then the map data is downloaded over the air (step 608).

As depicted in FIG. 5, once the map data is obtained, the devicegenerates a list of all labels to be rendered (step 610). Once thislabel list is created (and preferably sorted into alphabetical order formore efficient processing), the device checks to see whether any of thelabels are duplicated or redundant (step 612). If no duplicated(redundant) labels are found in the label list, the map is then rendered(step 614) without performing any stitching or reconstruction of pathsor features. Rendering of the map can include a step (not shown) ofverifying that the labels do not interfere with other labels. Forexample, this step of verifying that the labels do not interfere withother labels may involve a step of generating a collision-avoidancearray representative of the map to be rendered for provisionally testingpotential map positions prior to actually rendering the map. This“virtual rendering” enables the map application to ascertain that labelsdo not collide or overlap with other labels for which a map position hasbeen previously assigned.

As further depicted in the flowchart of FIG. 5, if duplicated orredundant labels are found in the label list at step 612, then, for eachduplicated label, then the device determines (step 616) whether thepaths (or other map features) match or connect, e.g. by looking atendpoints of path segments, as will be elaborated below with referenceto FIG. 7B. If the paths or features do not connect or otherwise fittogether, then the map is rendered without stitching the segmentstogether, i.e. labels are rendered for each of the segments orconstituent elements because these segments or constituent aredisjointed or disconnected and therefore require separate labelling. Onthe other hand, if, for any duplicated labels, the path segments orconstituent elements of the map features connect or match, then the pathsegments or constituent elements of the map features are reconstructed(“stitched together”) to form a reconstructed path or reconstructed mapfeature (step 618). Once the reconstructed path or reconstructed mapfeature is generated, the map can be rendered with a single instance ofthe map label, preferably centrally positioned along the entire lengthof the reconstructed path or centrally disposed vis-à-vis thereconstructed map feature (step 620). Rendering the map with the singleinstance of the map label should involve checking whether the labelinterferes or overlaps with any other label for which a label positionhas been designated. As noted above, this can be accomplished bygenerating a collision-avoidance array representing the map to berendered and then populating the array with label positions from highestpriority to lowest, checking that each successive label of decreasingimportance does not collide in the array with any previously assignedlabel positions.

For the purposes of this specification, “label” includes not only allconventional forms of labels, such as city names, street names, etc, butalso any symbols or icons, such as highway number icons, or symbols oricons used to denote airports, tourist information kiosks, campgrounds,ferry crossings, etc. on large scale (regional) maps or restaurants,hotels, bus stations, etc. on city maps.

For the purposes of this specification, “map feature” means a path,road, street, highway or other route and also includes features such asa body of water (river, lake, bay, strait, sea, ocean), an island, apark or other geographical feature that can be rendered from two or moreseparate sets of map data (i.e. vectors) for which individual labels areprovided (and which are thus potentially duplicated upon rendering).

FIG. 6 schematically depicts the process of reconstructing (“stitching”)paths and/or map features in order to efficiently generateaesthetically-labelled maps for being displayed on wirelesscommunications devices. By way of overview, map data (which includeslabel data) is obtained from a map server in the form of Data Entries(“D Entries”). Different layers of these D Entries are used to renderfeatures of the same type or class. Thus, for example, one layer of DEntries may be for lakes, rivers and bodies of water, while anotherlayer of D Entries may be for highways, roads and streets. This layeredimplementation enables context-filtering of desired or pertinent mapdata so that only desired or pertinent features are rendered onscreen.

In the example depicted in FIG. 6, the map is rendered from threeseparate D Entries (or three separate groups of P Entries from differentlayers). For the sake of illustration, the three D Entries (D Entry #1,D Entry #2, and D Entry #3) are rendered together to constitute the(composite) map. As each D Entry has its own (independent) label for“Main Street” as well as its own label for “Windy Lake”, simplyrendering the map data as a composite map would unacceptably result induplication of the labels, as shown in FIG. 6.

Even if any duplicated labels are suppressed, the resulting map, asdepicted in FIG. 7, would not be aesthetically pleasing because only oneof the three path labels would appear along its respective path segment(e.g. the Main Street label would appear, say, only along the first pathsegment), which is not necessarily centered. Similarly, only a singleinstance of the map feature label (e.g. Windy Lake) would appear on onlyone of the elements of the feature (e.g. the Windy Lake label wouldappear, say, on only the first constituent portion of the lake). Acorollary problem is that the label can only be displaced over a limitedrange corresponding to the segment or constituent element (ifrepositioning is mandated by a collision with another label). Since thelabel can only be repositioned over a limited range, the resultinglabelled map is aesthetically compromised.

These problems can be overcome by stitching or reconstructing paths (orother map features) to create reconstructed paths (or reconstructedfeatures), as depicted in FIG. 8. Since the path segments haveduplicated labels and connecting endpoints, the path segments arestitched/reconstructed to form a single reconstructed path.

In one implementation, this reconstruction (stitching) can beaccomplished in the manner described in FIGS. 9A-9C. Similarly, othermap features (such as the lake in FIG. 8) can be reconstructed, orstitched together, to form a single reconstructed feature.

For the reconstructed path, only a single instance of the label (e.g.“Main Street”) is rendered, preferably in a central position vis-à-visthe path (i.e. the most aesthetic place for the label). Since the pathhas been stitched together to form a single reconstructed path, thelabel can be displaced anywhere along the reconstructed path. Therefore,as shown by the dashed-line arrows in FIG. 8, the label can be displacedover a much greater range than was previously possible when the labelwas confined to being rendered somewhere along the limited range of itsoriginal path segment. In other words, not only can the label becentered vis-à-vis the “true” (from the viewer's perspective) center ofthe reconstructed path or feature, but the label can also be displacedsubstantially to avoid collisions with other labels.

Likewise, for the reconstructed map feature (in this example, the lake),only a single instance of the label (e.g. “Windy Lake”) is rendered,preferably in, a central, prominent location vis-à-vis the feature,provided it does not collide or interfere with another pre-existing orhigher-priority label. Furthermore, because of the reconstruction of thefeature, the feature is no longer composed of constituent parts for thepurposes of labelling. Accordingly, the label can be displaced over theentire range of the feature, not just over the constituent part withwhich the label was originally associated. This provides much moreleeway in finding a suitable position for a label on the map, i.e. alabel position that does not collide or interfere with any other label.In order words, this stitching technique enables labels to be renderedin preferred positions (e.g. centrally, prominently, aesthetically,etc.) while providing maximal leeway for displacing the label in theevent that it collides with another (pre-existing or higher-priority)label.

FIG. 9A schematically depicts the generation of a label list 700, inaccordance with one implementation of present technology, fordetermining whether any labels are duplicated in a given set of DEntries that are to be used to render the map. The label list 700, inthis implementation, is generated by the map application 500 using labeldata received wirelessly by the wireless communications device 202.

In the example shown in FIG. 9A, the label list 700 includes the list oflabel names itself (i.e. a field for storing the name of each labelinstance), a link field (indicating how, if at all, the label can belinked to any duplicate labels), a vector field (indicatingdirectionality of map data stored in vector format) and a flag field(indicating whether the data vector needs to be reversed to concord withthe directionality of a vector of the same label). Although each ofthese four fields of the label list is described in greater detailbelow, it should be understood that the details of this label list arepresented solely for the purposes of illustration. Persons of ordinaryskill in the art will appreciate that other implementations of labellists or equivalent algorithms can be used to determine label redundancyand whether endpoints of the paths or other non-path features of anyredundant labels match.

In the example presented in FIG. 9A, the label list 700 includes pathlabels “First Avenue”, “Main Street”, and “Second Avenue” as well as anynon-path feature labels, i.e. “Windy Lake”. As shown, multiple instancesof each label appear in the label list 700, representing each instancethat one of the D Entries used to render the map carries that particularlabel. Thus, in this example, the label “Main Street” is listed threetimes in the label list because each of the D Entries used to create themap contains its own instance of the label “Main Street”. Likewise,since each of the three D Entries contains the non-path feature label“Windy Lake”, this label is listed three times in the label list.Preferably, the label list is sorted alphabetically to streamline thealgorithm that searches for redundancies and performs the linking.

In the example depicted in FIG. 9A, the label list 700 includes a linkfield or link parameter that indicates for each label entry (each listedinstance of each label) what its relationship is with a previous orsubsequent label of the same name. Linking of labels can be accomplishedusing a standard linked-list construct for objects, which is well knownin the art. If a label appears only once in the label, i.e. has merely asingle instance, then it cannot be linked to another label, andtherefore its link parameter, or link field, is simply indicated as“None”. Thus, returning to the specific example presented in FIG. 9A,the path label “First Avenue” appears only once, and therefore its linkparameter is “None”. The same holds for Second Avenue, which appearsonly once. Its link parameter is thus also designated as “None.”

Unlike First Avenue and Second, the path label “Main Street” appearsthree times, and thus its link parameters need to determined.Determining link parameters (or link status) can be accomplished bycomparing endpoints of each link segment, as depicted in FIG. 9B. Asshown in FIG. 95, the endpoints (x1,y1) of the first path segment ofMain Street are compared with the endpoints (x2,y2) of the secondsegment of Main Street. If the endpoints (x,y coordinates) are equal (orat least match within a predetermined tolerance), then the segments areeligible to be stitched together. Accordingly, the link parameter/statusis updated to reflect the concordance of the endpoints of the pathsegments. In this example, the first instance of the Main Street labelshows that the link parameter is “Next” (meaning that the segment withthis label connects to the segment associated with the next label in thelist).

As depicted in FIG. 9B, the endpoints (x3,y3) of the second segment ofpath label “Main Street” are compared with the endpoints (x4,y4) of thethird segment of “Main Street” to determine whether these endpointcoordinates coincide. If the endpoints coincide (or match within thetolerance), as they do in this example, the link parameter is updated toindicate that the third label is linked to the “previous” label, i.e.the second label. Using this linked-list construct, the relationshipsbetween the first Main Street label and the second Main Street label andbetween the second Main Street label and the third Main Street label aredefined. In this example, the first Main Street label is linked to thenext label, i.e. the second Main Street label (and, conversely, thesecond Main Street label is linked to the previous Main Street label).The third Main Street label is linked to the previous Main Street labelas well (i.e. to the second Main Street label) As a result, all threelabels are linked together, meaning that the three path segments can bestitched together.

Likewise, the label list also accounts for linkage relationships betweennon-path map features such as the lake shown in FIGS. 6-8. Its label“Windy Lake” appears in each D Entry and thus three instances of thislabel appear in the label list. Again, by comparing endpoints orperimeter points, the constituent parts of the lake can be compared tosee whether they match or align. If so, the link fields for each WindyLake entry can be updated as was done for Main Street.

As further depicted in FIG. 9B, the label list 700 can include a vectorfield and a flag field. The map data is stored in vector format,allowing the vectors (data) to be packaged in small “chunks” tofacilitate OTA transmission and rendering. If the bounding box of each“chunk” of data, or D Entry, is small then it is quicker to intersectits bounding box with the screen's bounding box to determine if it needsto be rendered (and requested/transmitted if it not already cachedclient-side). Chunking up the data into small packages or D Entries,however, means that paths and other map features (each having their ownlabels) will likely extend into more than one D Entry. The foregoingtechnique effectively reconstructs the paths (or features) by checkingwhether the endpoints of path segments (or whether the constituent partsof features) coincide or fit together. A further problem that arisingwith the D Entries being in vector format is that the directionality ofone segment of a path (or feature) could be opposite to that of anothersegment even if their respective endpoints coincide. Prior to stitchingthese segments (or constituent parts) together, then, it is preferableto assess the directionality of the vectors defining the segments (orconstituent parts). This can be accomplished using a unit vectornotation such as a presented, by way of example only, in FIG. 9A. Inthis example, the First Avenue label is rendered using a unit vectorthat runs vertically download (in the y-direction) without anyhorizontal component (x=0). Thus, the vector is denoted as (0,−1). Themagnitude of the vector is not relevant, only direction. Comparison ofvector directionality is depicted, again by way of example only, in FIG.9C which shows the three segments of the path Main Street and theirassociated vectors. Assuming that the first segment of Main Street hasunit vector (1, −1), that the second segment has unit vector (1,0) andthat the third segment has unit vector (−1,0), then it is observed thatthe second and third segments have opposite directions, as shown in FIG.9C. Accordingly, this inconsistency in the directionality of twocontiguous segments that are eligible to be conjoined or stitchedtogether for the purposes of feature reconstruction is flagged in labellist 700. The flag indicates that the third segment of Main Street needsto have the direction of its vector reversed. Once all vectors have beenaligned by reversing any inconsistent segments of the path, the threesegments can be “stitched” or “spliced” together to generate thecontiguous, reconstructed path.

Optionally, when the reconstructed path is generated, the length of eachconstituent path segment and/or the total length of the reconstructedpath are stored. These values can be used to determine an initialstarting point for centering each label vis-à-vis the midpoint of thereconstructed path. Knowledge of these values also facilitatesrepositioning of the label when a potential label collision is detectedor foreseen. These values can be stored as further fields of the labellist 700. Labels can thus be rendered, or virtually rendered, withreference to the center of the reconstructed path, which is thepreferred technique. Alternatively, labels can be rendered (orrepositioned in the virtual rendering process) by virtually rendering alabel along a center of a middle segment (or the segment closest to themiddle of the onscreen bounding box) and then, if all of the label doesnot fit along that segment, checking whether the segment is spliced to afurther segment (i.e. checking whether a reconstructed path exists forthat label).

Similarly, when reconstructing non-path features (i.e. features that arenot lines but rather polygons), other dimensions such as, for example,the average horizontal width of the polygon feature, can be stored foreach of the constituent elements of the non-path map feature and for thereconstructed map feature, also for the purposes of facilitatingcentered labelling of the reconstructed feature.

The label list 700 depicted in FIG. 9A can be implemented using alabelPath object created for the path, containing the path data, thelabel and any other information used to render the label on the map.Every labelPath object would then be placed into a list sortedalphabetically according to the label associated with each path. Wheneach labelPath object is added to the list, a check is performed to seeif there are any other labelPath objects whose labels are identical tothe label of the path being added. If other labelPath objects are foundwith identical labels, the endpoints are compared and, if any match,then the labelPath objects are associated with each other using astandard linked-list construct, as alluded to above.

FIG. 10 is a screenshot of a street map of downtown Ottawa, Canadawithout stitching (reconstruction) of paths. As shown, many of thestreet labels are not centered onscreen. Some egregious examples are“Queen St”, “Albert St” and “Nepean St” which are far from beingproperly centered onscreen. In contrast, FIG. 11 is a screenshot of astreet map of downtown Ottawa, Canada with stitching (reconstruction) ofpaths. The labels on this map are centered vis-à-vis their respectivestreets. Note, in particular, how the path labels “Queen St”, “AlbertSt” and “Nepean St” are centrally located by first stitching the pathsegments constituting the entire path. Some repositioning(off-centering) may, of course, prove to be inevitable as a consequenceof having to avoid collisions with other labels. A collision-avoidancealgorithm will attempt to place the label centrally (at a midpoint ofthe path), if possible, but will then reposition the label, ifnecessary, to avoid collisions with other labels onscreen.

The foregoing method steps can be implemented as coded instructions in acomputer program product. In other words, the computer program productis a computer-readable medium upon which software code is recorded toperform the foregoing steps when the computer program product is loadedinto memory and executed on the microprocessor of the wirelesscommunications device.

This new technology has been described in terms of specificimplementations and configurations which are intended to be exemplaryonly. The scope of the exclusive right sought by the Applicant istherefore intended to be limited solely by the appended claims.

1. A method of displaying a map on a wireless communications device, themethod comprising steps of: obtaining sets of map data for renderingportions of the map on a display of the device, the map data includinglabel data for rendering labels on the map for identifying one or moremap features; generating a list of all the labels to be rendered on themap; for each duplicated label in the list, determining whether the mapfeatures associated with the duplicated labels connect on the map;generating a reconstructed map feature; and rendering a single instanceof the label for the map feature.
 2. The method as claimed in claim 1wherein the step of rendering the single instance of the label comprisesa step of rendering the label such that the label is aligned with amiddle of the reconstructed map feature.
 3. The method as claimed inclaim 1 wherein the reconstructed map feature is a reconstructed paththat is reconstructed from constituent path segments derived fromseparate sets of map data.
 4. The method as claimed in claim 3 whereinthe step of determining whether the map features associated with theduplicated labels connect on the map comprises a step of determiningwhether a first endpoint of a first path associated with the duplicatedlabel matches a second endpoint of a second path also associated withthe duplicated label.
 5. The method as claimed in claim 4 wherein thestep of rendering the single instance of the label comprises a step ofrendering the label midway along the reconstructed path.
 6. The methodas claimed in claim 1 wherein the step of generating the reconstructedmap feature comprises steps of: determining a direction of a data vectorfor each constituent set of map data that, when rendered, togetherconstitutes the reconstructed map feature; and reversing the directionof one or more data vectors so that all data vectors in thereconstructed map feature have a common direction.
 7. The method asclaimed in claim 3 wherein the step of generating the reconstructed mapfeature comprises steps of: determining a direction of a data vector foreach constituent set of map data that, when rendered, togetherconstitutes the reconstructed path; and reversing the direction of oneor more data vectors so that all data vectors corresponding to eachconstituent path segment in the reconstructed path have a commondirection.
 8. The method as claimed in claim 3 wherein the step ofgenerating the reconstructed path comprises a step of storing a lengthof each constituent path segment and a total length of the reconstructedpath.
 9. The method as claimed in claim 7 wherein the step of generatingthe reconstructed path comprises a step of storing a length of eachconstituent path segment and a total length of the reconstructed path.10. The method as claimed in claim 1 wherein the step of generating thelist comprises a step of sorting the labels into alphabetical order. 11.A computer program product comprising code adapted to perform the stepsof claim 1 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 12. Thecomputer program product comprising code adapted to perform the steps ofclaim 2 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 13. Thecomputer program product comprising code adapted to perform the steps ofclaim 3 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 14. Thecomputer program product comprising code adapted to perform the steps ofclaim 4 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 15. Thecomputer program product comprising code adapted to perform the steps ofclaim 5 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 16. Thecomputer program product comprising code adapted to perform the steps ofclaim 6 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 17. Thecomputer program product comprising code adapted to perform the steps ofclaim 7 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 18. Thecomputer program product comprising code adapted to perform the steps ofclaim 8 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 19. Thecomputer program product comprising code adapted to perform the steps ofclaim 9 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 20. Thecomputer program product comprising code adapted to perform the steps ofclaim 10 when the computer program product is loaded into memory andexecuted on a processor of a wireless communications device.
 21. Awireless communications device for enabling a user of the device todisplay a map on the device, the wireless device comprising: an inputdevice for enabling the user to cause the device to obtain map data forrendering the map to be displayed on a display of the device, the mapdata including label data for rendering labels on the map foridentifying one or more map features; and a memory for storing code toinstruct a processor to: generate a list of all the labels to berendered on the map; determine, for each duplicated label in the list,whether the map features associated with the duplicated labels connecton the map; generate a reconstructed map feature; and render on thedisplay of the device a single instance of the label for the mapfeature.
 22. The wireless communications device as claimed in claim 21wherein the processor renders the label such that the label is alignedwith a middle of the reconstructed map feature.
 23. The wirelesscommunications device as claimed in claim 21 wherein the reconstructedmap feature is a reconstructed path that is reconstructed fromconstituent path segments derived from separate sets of map data. 24.The wireless communications device as claimed in claim 23 wherein theprocessor determines whether a first endpoint of a first path associatedwith the duplicated label matches a second endpoint of a second pathalso associated with the duplicated label.
 25. The wirelesscommunications device as claimed in claim 24 wherein processor rendersthe single instance of the label midway along the reconstructed path.26. The wireless communications device as claimed in claim 21 whereinthe processor determines a direction of a data vector for eachconstituent set of map data that, when rendered, together constitutesthe reconstructed map feature and then reverses the direction of one ormore data vectors so that all data vectors in the reconstructed mapfeature have a common direction.
 27. The wireless communications deviceas claimed in claim 23 wherein the processor determines a direction of adata vector for each constituent set of map data that, when rendered,together constitutes the reconstructed path and then reverses thedirection of one or more data vectors so that all data vectorscorresponding to each constituent path segment in the reconstructed pathhave a common direction.
 28. The wireless communications device asclaimed in claim 23 wherein the processor causes the memory to store alength of each constituent path segment and a total length of thereconstructed path.
 29. The wireless communications device as claimed inclaim 27 wherein the processor causes the memory to store a length ofeach constituent path segment and a total length of the reconstructedpath.